ReutersBoeing 777 Malaysian Airlines with the registration number 9M-MRO flies over Poland February 5, 2014.

Malaysia Airlines has now confirmed that Flight 370 was carrying lithium-ion batteries in its cargo hold, the Daily Mail reports. This new fact could bolster the theory that the plane was brought down by a fire rather than a hijacking or other malfeasance.

It has now been more than two weeks since Malaysia Flight 370 disappeared. No confirmed trace of the plane has been found, and investigators still appear to be mystified about what happened.

The two prevailing theories are that the plane was commandeered by the pilots or hijackers or suffered a fire or other mechanical problem.

Both theories fit some but not all of the supposed facts that have been released thus far. The fire theory, for example, is undermined by the lack of any apparent distress call. And no motive has been unearthed that might explain the hijacking/commandeering theory, especially given the likelihood that the plane then later crashed somewhere in the Indian Ocean.

On Friday, Malaysia Airlines CEO released some new information that could bolster the fire theory. Four days after denying that the plane had carried any hazardous materials, the CEO admitted that it was carrying a shipment of lithium-ion batteries in its cargo hold.

These batteries, which commonly power cell phones and other gadgets, have occasionally caused fires, including on airplanes. The Mail reports data from the FAA citing 140 incidents in the last 25 years involving lithium-ion batteries. At least two major crashes in the past two decades, meanwhile, have been caused by on-board fires, including a Swissair flight in 1998 and a UPS cargo plane in 2010.

Earlier this week, a former pilot named Chris Goodfellow articulated the fire theory, explaining how the plane's turn to the west could have been a standard attempt to head toward the nearest airport for an emergency landing. The plane's new heading put it on a course straight for Pulau Langkawi, a major airport in northern Malaysia.

Billie Vincent, a former Federal Aviation Administration security official, has also argued that the facts fit a fire. “The data released thus far most likely points to a problem with hazardous materials," Vincent told Air Traffic Management.net. "This scenario begins with the eruption of hazardous materials within the cargo hold – either improperly packaged or illegally shipped – or both.”

Malaysia Airlines says the batteries in the cargo hold were properly packed.

Vincent also suggests that the strange altitude readings that Malaysian investigators say they captured on radar—an ascent to 45,000 feet and then a descent to 25,000—could be explained by a fire. The pilots might not have been able to see the controls in the cockpit, Vincent said, and thus ascended higher than they intended. And, later, they might have been trying to get the plane to an altitude at which they could vent the plane and slow the progress of the fire, as well as prepare for an emergency landing.

Malaysian investigators say they believe that the plane was commandeered, and one fact in particular they have released does not fit the fire theory. They say that the plane changed its course prior to a final radio communication in which the co-pilot said "good night" to air-traffic control — a routine call that made it seem like everything was fine.